Treating hydrocarbon oils



y 1931. w. K. HOLMES TREATING HYDROCARBON OILS Filed Aug. 13, 1925 Ptented T2, 1931 it: STATES rarer orrlcr.

TREATING HYnRocABBoN OILS Application filed August 13, 1925. Serial No.49,931.

This invention relates to the conversion of higher boiling hydrocarbons into lower boilmg products such as gasoline, the like.

Ithas been sought to carry on the pyrogenic decomposition of hydrocarbon oils by a continuous method of operation in which the oil tobe converted is continuously charged to the system. A fundamental defect or limitation of such attempted continuous processes is that it is impossible during a run to efi'er t a clean separation between the unconverted liquid oil and the heavy carbon-forming hydrocarbons and carbon formed in the reaction and, thus, even though tar or residue be withdrawn from the system during a run in a "conventional manner, there is a tendency, as the run is continued, toward the concentration of the carbon-forming constituents and carbon which imposes a serious limitation upon the 1 length of runs.

are formed, in addition to the lighter hydrocarbons which are ordinarily evolved as a .vapor, certain polymerized constituents 'or 25 heavy hydrocarbons which are readily decomposed to yield free carbon. In the continuous method of operation it is, as stated, practically impossible to remove all of these bodies from the converter by drawingoif tar in the conventional manner, due to the difiiculty in obtaining complete separation of these bodies from the other liquid oil. The result is that as a run is continued these constituents tend to accumulate in the converter and the heat employed in the cracking operation readily decomposes them into free carbon. As a run is continued there is thus an inevitable tendency toward the accumulation of heavy carbon-forming oils and carbon or coke which necessitates stoppage of the run.

T have found that the length of runs may be materially increased by periodically subjecting the converters to a temporary flush ing operation. Thus, by sufliciently increasing the rate of charge to the cracking zone and increasing the amount of tar withdrawn therefrom, the heavy residual products may be readily removed rom the system.

In practicing the invention the oil to be naphtha and superatmospheric pressure and at a tempera- In the cracking reaction there 7 converted is introduced into a converting chamber, or preferably into a series of converters, wherein the Oll is maintained under ture adequate for'an efiicient rate of cracking. Tar or residue is withdrawn from the converters either practically continuously or intermittently and fresh oil is admitted in substantially a continuous manner so as to maintain a quantity of 'oil in the converters. It facilitates the removal of tar and contributes to the smooth operation of the process to subject the oil undergoing conversion to agitation or stirring.

Distillate is preferably taken .off directly from the converters, although if desired the distilling operation may be'car ried onseparately from the cracking per so by Withdrawing liquid containing the lighter hydrocarbons formed and subjecting this liquid to distillation for the recovery of gasoline. As stated, however, it is preferable to carr on distillation concurrently with the cracking operation and it is desirable to produce a suitably fractionated product adapted for the particular grade of gasoline desired without the necessityof having to subsequently distill the distillate obtained from the con verters. Suitable fractionating means is, therefore, provided to fractionate the evolved vapors so that a distillate of desired boiling point may be taken off directly from the cracking apparatus.

,The operation is thus continued, fresh oil being supplied to the converters and distillate and residue being removed. As the run continues there is a tendency, as heretofore explained, for heavy carbon-forming prodnets to collect in the converters. The accumulation of these heavy bodies may 'beobserved by an increase in the s ecific gravity of the tar samples withdrawn, y an increase in the amount of powerrequired for operating the stirring or scraping mechanism an by a lowering of the temperature in the bottom of the converters where the heavier products accumulate. This accumulation of heavy bodies in the stills is. in some instances perceptible after the stills have been on stream for a few hours but in most cases, i

ASSIGN'OR, ,IBY MESNE ASSIGNMENTS, To THE N. Y., A CORPORATION OF DELAWARE In carrying on the flushing operation the rate of charge and the rate of withdrawal may be so increased that the cracking operation is for a time suspended or at least the rate of distillate formation 'reduced; in fact the flushing may be carried out to such an extent as to stop for a time the flow of distillate. In general, however, I do not find it necessary to conduct such. an extensive flushmg out action and have 'found in practice" that it is possible to carry out the scrubbing or cleaning operation in such a wayas to not seriously impede the cracking operation and formation of distillate. Thus forexample,

when the normal rate of charge is'around 40 or barrels per hour, witha converter ca "pacity OfSOIl'lG 300 or 400 barrels, the rate during. the flushing operation may be in creased a few barrels, but usually not over 10 barrels, without reducing the rate of distillate more than=2 or 3 per cent. It is desir-' able to increase the amount of heating commens'urate with the increased charge so as to avoid unduly. lowering the temperature of the oil undergoing conversion,- whereby the rate of conversion and distillation is not inaterially reduced.

The flushingl operation is carried on for a time until'the v moved from the system, the operation last eavier' products have been re"- ing in some'cases only a few minutes but in general, for periods of several hours, for example, five to eight-"hours. The rate of charge is then dropped back to normal and the rate'of tar draw-o'fi reduced so as to maintain the re uired liquid level in the stills. During. t efiushing operationthe ravity of the tar is ordinarily lighter than t at normally drawnofi' but after thefiush- ISO .ing has ceased the gravity is soon normal again and the distillate rate also assumes normal proportions; The regular operation is then resumed. .until. the stills again runheavy when the flushing operation is repeated. Ordinarily it is only necessary to flush at intervals of about three or four days However, the fre uency of the flushing operation, as well as't e extent andcharacter of same, depend upon various conditions of operation and more es ecially upon the character of charging stoc employed.

By thus periodically cleaning the stills of the heavy carbon-forming products it is possible to maintain them on stream for considerable periods of time... Pressure stills may be kept in continuous operation in this manner for several months at a time. So far as I am aware it has been impossible prior to my invention to conduct extended runs of this character. v

In the preferred embodiment of the invention the oil to be treated is passed through a coil or heating element of restricted cross section wherein the oil in transit is raised to a cracking temperature, the rate of flow being so regulated that, although .the oil is heated to the cracking temperature desired,

it is removed from the coil before any material decomposition occurs. The heated oil is discharged into a converter, or preferably a series of converters, wherein quantities of oil are maintained at acracking temperature under superatmosph'eric pressure. The 'oil undergoing conversion is subjected to agitation or stirring which tends .to prevent deposition of carbon on the walls of the converters and assists in maintaining the con-.

tents in a suitablgeliquid condition so that the residue may readily drawn off. In

carrying .on thefiushing operation the rate of charge through the heating coil is increased slightly and preferably also the amountof heat sup-plied to the coil is increase-d, while'increased quantities of liquid are drawn off from one or more of the converters;

In order to describe the invention more specifically I have, by way of example, shown 1n the accompanying drawing an apparatus.

adapted for practicing theinvention, the drawing vation.

In'the drawing 10 represents a battery of stills consisting of the stills 10a, 10b, 10c, and

10d, interconnected bysuita-ble vapor equalizing lines 11 and liquid level lines 12. The stills are shown mounted in a furnace" 13 although, if desired, they may be insulated to being a diagrammatic sectional eleretard or prevent loss of heat by radiation, the necessary heat for the cracking operation being supplied by sufiiciently heating the oil prior to its introduction to the stills. Each still is provided with a shaft 14 carrying a plurality of scrapers or stirring elements 15 which operate to agitate the contents of the stills and, if desired, to scrape the .walls thereof and thus remove any carbon or coke deposited thereon. The shafts 14 are shown connected by cooperating bevel gears 16 to a common shaft 17 which is suitably power driven.

18 represents a coil or conduit of restricted cross section suitably mounted in a furnace 19, the furnace being preferably adapted to heat the oil to a cracking temperature. A pump 20 is adapted to draw oil from a suitable source and force the oil through a charging line 21'to the heating coil 18. If desired, the oil before being introduced into the coil 18 may be passed through suitablepreheaters or economizers heated, for example, by

from the furnace 13, or from both of these furnaces, or by such other heat exchange ape pa'ratus' as may be desired.

The heating coil is provided with an outlet 22 adapted to conduct the heated oil to one or more of the stills 10. As illustrated the pipe 22 is shown as having valved branches I 23 and 24,. which branch lines communicate,

' respectively,

. the coil is drawn by a valved pi liquid while manipulating the municate with a commontar line 33.

. cooling requir with valved branches 25 and 26, and 27 andf 28, which-lead, respectively, to stills 40a, .105, 100i indlod. By properly valves in the lines 23, 24, it is possible'to introduce 25, 26, 27, and 28 to any or all of the stills the charging stock as maybe desired.

The stills are. provided with valved tar lines 29, 30, 31 "and 32 which preferably 0%:-

e tar line 33 may, if desired, lead to a suitable exchanger suppliedwith charging stock the pipe 21 so that the heat of the tar may bevutiliz'ed in imparting heat to the charging stock.

The battery of stills is provided with a vaper line 34 tha t extends'to a fractionating be in the form of a" tower 35 which may bubble tower, packed-tower, or other suitable fractionating column. tower 35 is equipped with a -vapor line 36 which leads to a reflux eondenser37, a back trap line 38 beingprovided for conductingthe reflux condensate to the .tractionating column 35.

The reflux condenser is equipped. with. a

coolin coil 39 and the cooling medium-for the charging line 21 and returne by valved pipe 41 to t e charging line. The charging stock may thus be utilized in furnishing the d to supply the iractionating' device 35 with the necessary cooling or reflux v at the same time the charge is preheatedto a certain extent. r

The line 21', intermediate the points'of 1 ur cture of pipes 39 and40, is PTOVldBdY WIth a valve 42 so that, if desired,a portion of the charge may be passed'directlythrough the [line 21 to the pipe 18 crto such other econo' through the coil. 39

mizer'or preheating apparatus as'may be'decondenser waste heat from the furnace 19, or-

' liquid.

The fractionating e from c line 40, coil 39 and e valves in the lines 40 and degree of cooling and,

- 1y regulate the boiling point of the fraction which passes off as a vapor from the reflux 37. A pipe 43 is provided for conducting this vapor to a suitable cooling coil 44, the outlet 45 of which extends to a receiving drum- 46 having a gas outlet and condensate line 48.

The pump 49 illustrated'is adapted to return to the heating coil or charging line 21 the 'hot condensate that collects in the bottom of the 'fractionating column 35. The pump is equipped with surge lines 50 interposed between the pump cylinder 49 and the chambers 51 and adapted to rotect the pump piston andpacking from t e hot bottom of the fractionating' device 35 to branch lines 53 which communicate with the valve chambers 51.; The discharge line embraces the branch pipes 54 which extend from.

the'valve chambers to the discharge main 55 i that communicates with the charging line 21.

In the preferredm ethod'of practicing the invention with the lustrated, the oil to be treated, after having been passed through such heat exchangers and preheaters as may be desired, is introduced to theheating coil 18. The oil in transit through this coil is raised to a cracking temperature and is then assedthrough line 47 An inflow line 52 extends from the Y particular apparatus llthe line 22 and itswconnected ranch lines to Y the battery of stills 10. It is'general-ly prefenable to charge the oilinto one or more of the stills of the battery and draw tar frbm the other stills of the battery. Thus with the valve in the line 24 closed and the valve inthe line 23 open the heated oil may be passed through the line 23 and itsbranches to either or both of the stills 10a and 105. After op-' erating conditions have been established the bulk of the tar removed is drawnfthrough lines 31 and 32 from stills 10a and 10d. Or dinarily, since the oil passes in succession from the charging stills 10a and 10b, first to still the tendency still 100 and t en to is for the oil in the latter still to reach a more advanced stage of decomposition; consequently it is best to remove the bulk oi the tar-from this still. A Tar is removed-either by cracking the valves in the lines 31 and'32 for the-continuous removal oi residue or by tak ing shots from these stills from time to time as maybe necessary.

The evolved vapors pass 34 into the iractionating column 35 wherein they are fractionated to the desired degree. The heavier fractions, or

those of higher boiling point than desired, are removed from the column 35 by the surge pump 49 and thus returned to ment. The vapors are conducted by the pipe 38 to the reflux condenser 37 wherein a' portion thereof is condensed while the remain ing vapors are-removed by thevapor line 43 to the condenser coil 44. The charge of. oil

through the line the cracking zone for retreatbeing introduced to the system by the pump,

20, and such portion of thecharge as may be necessary, is by-passed through lines 40 and 41 through the coil 39. It is to be understood that the amount of oil thus passed through the coil 39 is varied during the run as conditions may require so as to control plained, the rate of charge to the heating coil 18 and consequently to the battery 10 1s in- 'creased'and' increased quantities of tar'or residue are drawn oil from the stills.

It is best to determine the gravity at which it is desired to'hold the tar regularly withdrawn fromv the system, this gravity depending upon the particular chargin'gstock employed, the amount of cracking desired,

and proportion of distillate-to be removed,

and the length of run desired. ,Whenever the gravity becomes unduly heavy, that is,

heavier than thelimit determined upon, the

flushing operation is carried on. As heretoforei explained the need for flushing is also shown, when employing stirring, agitating or scraping mechanism in'the converters, by an increase in the amount of power required for operating-such mechanism. 'A lower-mg of the temperature in the bottom of the converters, where the heavy carbonaformlng 0118 and carbon tend to collect, may also indicatethe need for flushing. .Thus, for example,

when the usual operating temperatures 1n the bottom of the converter are around 760 F.- to 800 F., a drop during a run to approx:

imately 720 F., particularly when there is not a correspondi'ng' drop in temperature in th'e: ;.other portions ofthe converter, shows the need for flushing,

In carrying on the flushing operation the oil may be charged into the stills 10a. and 10b and residue drawn oil from one or both of the stills 100 and 10d.. In'some cases it is advantageous to charge directly into the still or stills in which the heavy carbon-forming oils have collected. Thus the valve in the-line 23 may be closed, the valve in the line 24 opened and the oil passed through the line 24 and its branches into one'or both of the stills 100 and 10d, tar-being drawn 05 through lines. 31 and 32 as usual. In this way the flushing liquid is'conducted directly to the still or stills where it'is most needed.

By carefully'regulating the temperature in the furnace 19 and the rate of charging it'is possible to deliver to the stills orsconverters 10 oil that'has been heated to a crack in'g temperature without any material deneoaeee composition having taken place. This meth- 0d of operating keeps the tubular heater 18 substantially free fromcarbon or coke formations, even though operated for long periods of time. And by periodically flushing out the stills 10, or such of them as may be necessary, not only is the formation of carbon or coke deposits in the converters retarded or prevented but'any carbon deposits that are formed may be eliminated. In this way the operation is so conducted that in no part of the apparatus are injurious deposits of coke or. carbon formed so that the stills may be kept on stream for extended periods of time. During the flushing periods it .is-usually desirable to increase the heating somewhat in order that the normal operating temperature-and rate of distillation shall not be unduly lowered;

By way of example, it may be stated that runs of several monthsduration have been made by using as charging stock gas oil of around 30.0 Beaum gravity and having a mean boiling point of 580'F.600 F., or thereabouts, maintaining the outlet of the coil 18 at about775 F. to 800 F, or some- What higher, normally holding the stills or converters at about 760 F..to 800 F., using pressures of 200-300 pounds in the stills, taking oil distillate Beaum gravity and normally drawing ofl' tar or pressure bottoms 'of about 16-23 Beaum gravity, whileperiodically subjecting the stills totheflushing operation described herein. The tar withdrawn contained only about 25% of free carbon.

The practice of the invention has resulted in reducing the percentage of coke formed approximating 55-65 perbarrel of-charge to such an extent as to I make possible the extended runs.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without "departing from the spirit and scope thereof, and therefore, only such limitations should be imposed. as

are indicated in the appended claims.

What I claim is:

hydrocarbon oils into lower boiling products that comprises passing a stream ofoil under pressure through aheating coil and delivering it into an enlarged;- chamber Wherecracking, distillation, and carbon deposition are effected, applying heat to the coil to raise the oil in transit to a cracking temperature 1; The process of converting high boiling- I maintain the rate of distillation from the hand this 6th day of August,

chamber and the temperature of the oil emerging from the exit of the coil.

2. The process of converting higher boiling hydrocarbon oils into lower boiling ones that comprises subjecting a body of liquid oil to distillation at cracking temperatures and superatmospheric pressure, normally charging fresh oil to the still and withdrawing tar and distillate under conditions to maintain a given yield of distillate and agitating the body of oil to maintain any carbon formed in suspension in the liquid, periodically subjecting the still to a temporary flushing by increasing the charge above the normal rate and withdrawing increased quantities of tar while continuing the agitation to thereby remove from the still any accumulations of suspended carbon and heavy carbon-forming hydrocarbons, and after each flushing operation restoring approximately the normal rate of charge and tar removal to thereby maintain approximately the given yield of distillate with the still on stream for an extended period of time.

In witness whereof, I have hereunto set my 1925. WILL K. HOLMES. 

